1. Field of the Invention
This invention relates to a surgical tool, and more particularly, it relates to a surgical implant inserter compressor for implanting a surgical implant.
2. Background of the Invention
In the field of surgical implants, it is necessary to sometimes use a tool to hold the implant components when implanting and mounting them on bone, such as a cage that is mounted between vertebrae or plates that are mounted onto the spinous processes. For example, in some spinal surgeries, at least one or a plurality of plates are mounted or implanted on adjacent spinous processes to facilitate fusing, aligning or maintaining a relationship between these bones. One type of implant is shown and described in U.S. Patent Publication 2011/0172711, which is incorporated herein by reference and made a part hereof.
In the past, a typical tool for inserting these types of implants operated similar to a traditional pair of pliers in that the jaws of the tool pivoted about an axis and moved along an arcuate path when they opened and closed. One problem with using a tool of this type with the plates mentioned is that during mounting, any plates that were mounted on the jaws of the instrument did not engage the bone, such as the spinous processes, at substantially the same time or with the same amount of force. Unfortunately, this sometimes resulted in an uneven distribution of the forces with which the tool forced the plates into engagement with the spinous processes. This is especially true if the spinous processes were not of the same size or thickness or did not share a common longitudinal axis. This is illustrated in FIG. 8D. Notice that while the top spinous process SP1 shown in that figure is captured between the plates and if the surgeon desired to force the plates together until the bottom of the plates (as viewed in FIG. 8D) came into contact and engaged the lower spinous process in that figure, then the upper part of the plates shown in FIG. 8D would apply a greater force on the first spinous process SP1 than the force with which the lower part of the plate would apply to the second spinous process SP2. This could cause overstressing of the upper spinous process SP1. Alternatively, the lower part of one or both plates may not engage the spinous process at all in which case either one or both plates would not be locked, for example, to the lower spinous process SP2 as illustrated in FIG. 8D. This effect is referred to as “stress shielding”, such as when the first spinous process SP1 shields the second spinous process SP2 from being engaged by at least one of the first or second plates in the illustration. Obviously, this can have undesired results, as the plate(s) not being locked into the first and second spinous processes SP1 and SP2.
What is needed, therefore, is a system and surgical implant inserter compressor that enables at least one or a plurality of surgical implants, such as plates, to engage the bones to which they are going to be affixed or mounted with a substantially common or equal amount of force and which distributes the clamping forces substantially evenly.